DeCastro was carted off the field with what Steelers coach Mike Tomlin later called a "potentially severe" right knee injury during the first quarter of a 38-7 victory over the Buffalo Bills.

DeCastro, the Steelers' first-round draft pick, didn't return to the game, and Tomlin said afterward that the rookie would undergo an MRI to determine the severity of the injury.

On the Steelers' second drive of the game, DeCastro was tangled up with Bills defensive tackle Marcell Dareus on a pass play when Pittsburgh tackle Marcus Gilbert landed on the back of DeCastro's right leg.

Trainers helped DeCastro to one foot before he was carted off the Ralph Wilson Stadium turf, which quarterback Ben Roethlisberger blamed for the rookie's injury.

"Well, I just saw him, (and his) spirits are high," Roethlisberger told NFL.com and NFL Network's Kimberly Jones at halftime. "We don't obviously know -- well, I don't know what the official word is. This is a great field, but it's field turf," Roethlisberger said of Ralph Wilson Stadium's A-Turf, installed last year, "and it's just killing guys because they can't get their feet out of the ground, and it's just another reason we should get rid of field turf."

Tomlin and the Steelers used April's draft to rebuild an offensive line that caused problems for Roethlisberger last season. After selecting DeCastro out of Stanford with the No. 24 overall draft pick, the team used its second-round choice on offensive tackle Mike Adams from Ohio State. Both have gotten off to a slow start this preseason.

UPDATE:Steelers defensive end Brett Keisel also left the game with what Tomlin described afterward as a mild high ankle sprain.